Microbiology Lecture 6: Neisseria
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Questions and Answers

Which of the following outer membrane proteins prevents phagosome-lysosome fusion in neutrophils?

  • Por proteins (correct)
  • IgA1 protease
  • Opa proteins
  • Rmp (Protein iii)

    • How does the lipooligosaccharide (LOS) of gonococci differ from the lipopolysaccharide (LPS) of other Gram-negative bacteria?

  • It has longer O-antigen side chains
  • It has shorter O-antigen side chains
  • It is more toxic than LPS
  • It lacks the O-antigen side chains (correct)

    • What is the primary site of infection in women with gonococcal infection?

  • Vagina
  • Urethra
  • Uterine tubes
  • Endocervix (correct)

    • What is the consequence of gonococcal salpingitis in 20% of women?

    <p>Infertility</p> Signup and view all the answers

    What is the function of Rmp (Protein iii) in gonococci?

    <p>Associating with Por in the formation of pores</p> Signup and view all the answers

    How do Opa proteins contribute to the pathogenesis of gonococcal infection?

    <p>By mediating adhesion to host cell receptors</p> Signup and view all the answers

    What is the endotoxic effect of lipooligosaccharide (LOS) in gonococcal infection?

    <p>It is responsible for the toxicity in gonococcal infection</p> Signup and view all the answers

    What is the common consequence of urethral infection in men with gonococcal infection?

    <p>Painful urination</p> Signup and view all the answers

    What is the typical morphology of Neisseria species?

    <p>Gram-negative cocci in pairs</p> Signup and view all the answers

    What is the primary purpose of Kovac's oxidase test in identifying Neisseria?

    <p>To identify the presence of cytochrome oxidase</p> Signup and view all the answers

    What is the optimal growth condition for Neisseria species?

    <p>Aerobic conditions with complex organic substances</p> Signup and view all the answers

    What is the function of pili in Neisseria gonorrhoeae?

    <p>To increase resistance to phagocytosis</p> Signup and view all the answers

    What is the typical colony morphology of Neisseria species on enriched media?

    <p>Convex, glistening, elevated, and mucoid</p> Signup and view all the answers

    What is the effect of Kovac's reagent on Neisseria species?

    <p>It turns Neisseria into dark purple</p> Signup and view all the answers

    What is the typical size of Neisseria species?

    <p>0.8 µm in diameter</p> Signup and view all the answers

    What is the atmosphere required for the growth of Neisseria species?

    <p>5% CO2 and 95% O2</p> Signup and view all the answers

    What is the primary route of transmission of gonococcal ophthalmia neonatorum?

    <p>Acquisition during passage through an infected birth canal</p> Signup and view all the answers

    What is the primary purpose of blood culture in the diagnosis of gonorrhea?

    <p>To check for the presence of the bacteria in systemic illness</p> Signup and view all the answers

    What is the advantage of using nucleic acid amplification tests in the diagnosis of gonorrhea?

    <p>It provides a more rapid result compared to culture</p> Signup and view all the answers

    What is the recommended treatment for uncomplicated gonorrhea?

    <p>Ceftriaxone (250 mg) given intramuscularly as a single dose</p> Signup and view all the answers

    What is the primary way to reduce the infection rate of gonorrhea?

    <p>All of the above</p> Signup and view all the answers

    What is the most common complication of meningococcemia?

    <p>Meningococcal meningitis</p> Signup and view all the answers

    What is the purpose of using a modified MTM with antibiotics in nasopharyngeal cultures?

    <p>To inhibit the growth of contaminants</p> Signup and view all the answers

    What type of medium is used to streak pus or mucus specimens for culture?

    <p>All of the above</p> Signup and view all the answers

    What is the purpose of Gram-stained smears in the diagnosis of meningococcemia?

    <p>To show the typical arrangement of Neisseria meningitidis within polymorphonuclear leukocytes</p> Signup and view all the answers

    What is the consequence of untreated gonococcal ophthalmia neonatorum?

    <p>Blindness</p> Signup and view all the answers

    What is the significance of antibacterial activity in serology?

    <p>It is used to detect the bactericidal activity of antibodies</p> Signup and view all the answers

    What is the recommended treatment for possible concomitant chlamydial infections?

    <p>Azithromycin (1 g) orally in a single dose</p> Signup and view all the answers

    What is the purpose of taking specimens of spinal fluid in the diagnosis of meningococcemia?

    <p>To perform smear, culture, and chemical determinations</p> Signup and view all the answers

    What is the significance of petechiae in meningococcemia?

    <p>They can be used to obtain specimens for smear and culture</p> Signup and view all the answers

    What is the primary purpose of applying 0.5% erythromycin ophthalmic ointment or 1% tetracycline ointment to the conjunctiva of newborns?

    <p>To prevent gonococcal ophthalmia neonatorum</p> Signup and view all the answers

    What is the unique characteristic of Neisseria meningitidis that distinguishes it from gonococci?

    <p>Utilization of maltose</p> Signup and view all the answers

    What is the percentage of healthy individuals that can be asymptomatically colonized by Neisseria meningitidis?

    <p>5-10%</p> Signup and view all the answers

    What is the primary role of pili and outer membrane proteins in Neisseria meningitidis?

    <p>Playing a key role in colonization as adhesins</p> Signup and view all the answers

    What is the function of lipooligosaccaride in Neisseria meningitidis?

    <p>Causing fever and septic shock in systemic infection</p> Signup and view all the answers

    Which of the following serogroups of Neisseria meningitidis are associated with disease in humans?

    <p>A, B, C, X, Y, and W-135</p> Signup and view all the answers

    What is the mechanism by which Neisseria meningitidis is transmitted from one person to another?

    <p>Through respiratory droplets</p> Signup and view all the answers

    What is the role of capsular polysaccharide in Neisseria meningitidis?

    <p>Conferring resistance to serum bactericidal activity</p> Signup and view all the answers

    Study Notes

    Characteristics of Neisseria Species

    • Neisseria species are Gram-negative cocci, usually occurring in pairs to form diplococci
    • There are two medically important species: Neisseria gonorrhoeae (gonococci) and Neisseria meningitidis (meningococci)
    • Other species are members of normal human respiratory tract microbiota, and either rarely or never cause disease

    Typical Neisseria Characteristics

    • Gram-negative, non-motile, kidney-shaped diplococcus
    • Bacterial cells are about 0.8 µm in diameter
    • Grow best under aerobic conditions
    • Oxidize carbohydrates, producing acid but not gas
    • Fastidious, growing on media containing complex organic substances such as heated blood, hemin, and animal proteins
    • Require an atmosphere containing 5% CO2
    • Sensitive to desiccation, moist heat, sunlight, and many different disinfectants

    Identification Tests

    • Kovac's oxidase test: determines the presence of cytochrome oxidase, which causes Neisseria to turn dark purple when treated with Kovac's reagent
    • Other identification tests: Gram-stained smear, culture, coagglutination, immunofluorescence staining, and further laboratory tests

    Virulence Factors of Neisseria

    • Pili: hair-like appendages that enhance attachment to host cells and resistance to phagocytosis
    • Outer membrane proteins:
      • Por proteins: affect intracellular killing of gonococci within neutrophils and confer resistance to bactericidal activity of normal human serum
      • Opa proteins: mediate adhesion of gonococci to host cell receptors
      • Rmp (Protein iii): associates with Por in the formation of pores in the cell surface
    • IgA1 protease: inactivates IgA1 antibodies, which are the main mucosal antibody of humans
    • Lipooligosaccharide (endotoxin): differs from lipopolysaccharide (LPS) of other Gram-negative bacteria, lacks long O-antigen side chains, and is responsible for endotoxic effects in gonococcal infection

    Pathogenesis and Transmission of Neisseria

    • Transmission:
      • Neisseria gonorrhoeae: sexual contact, birth (infection of newborns during passage through an infected birth canal)
      • Neisseria meningitidis: respiratory droplets, bacteria can colonize around 5-10% of healthy individuals asymptomatically
    • Pathogenesis:
      • Neisseria gonorrhoeae: attacks mucous membranes of different sites of the body, resulting in acute suppuration, tissue invasion, chronic inflammation, and fibrosis
      • Neisseria meningitidis: colonizes the nasopharynx, reaches the bloodstream, and spreads to the meninges, causing bacteremia, meningococcemia, and meningitis

    Diagnosis of Neisseria Infections

    • Neisseria gonorrhoeae:
      • Specimens: pus and secretions from urethra, cervix, rectum, conjunctiva, throat, or synovial fluid
      • Smears: Gram-stained smears of urethral or endocervical exudates reveal many diplococci within pus cells
      • Culture: pus or mucus specimens can be streaked onto enriched or selective medium, incubated at 37°C in 5% CO2
    • Neisseria meningitidis:
      • Specimens: blood, spinal fluid, nasopharyngeal swab cultures
      • Smears: Gram-stained smears of the sediment of centrifuged spinal fluid or petechial aspirate often show typical neisseriae within polymorphonuclear leukocytes or extracellularly
      • Culture: blood and cerebrospinal fluid specimens are plated onto agar culture media, modified MTM with antibiotics for nasopharyngeal cultures
      • Serology: antibodies against capsular polysaccharides can be used as a detection test, detected by latex agglutination or hemagglutination tests or by bactericidal activity

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    Lecture 6: Neisseria - Warith Al-Anbiyaa University

    Description

    This lecture covers the characteristics and diagnosis of diseases caused by Neisseria species, including Neisseria gonorrhoeae and Neisseria meningitidis.

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